I would say that the Nether is an extremely dicey prospect for more novice players. First, you have to acquire obsidian, and players who don't know the tricks for creating it artificially will be stuck until they get some diamond on their hands.
Then, once they get to the Nether, they'll be dodging fireballs from Ghasts all over the place. It's not a region I've been interested in building in, either. While it can be visually impressive, there's a "sameness" about it that makes its vistas less interesting overall than the surface world.
I think the Nether is too tough to be used in any practical way by more novice players unless they go Peaceful. The difficulty slider in this game doesn't really work, as far as I'm concerned. You have Peaceful, and then varying degrees of Hard.
In the spirit of Minecraft, I'd still love it if the game gave you a lot of fine-tuning options. Let you spawn worlds using various sliders, pick which mobs you want to spawn and how often, change the game rules, etc. etc. Imagine having a checkbox that allows monsters to spawn in daylight and not have them burn to death. You could have options to make the game harder or easier--depending on your preference.
That's kind of my main beef with the game. It's very open-ended as to what you can build and how you explore, but that sort of freedom is sorely lacking on the game mechanics side.